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Activity 2.1 Logic Crash Course

Introduction

Computers aren’t limited to performing arithmetic calculations. We are able to program computers to make decisions using logical expressions. When a computer can make decisions, it’s able to determine different outcomes in a program. Here are a few example scenarios:

• If you sign in to an application, the app will determine if you signed in with a valid account or not.
• When viewing mature games on Steam, the app needs to verify if you are old enough to view the game or not.
• If you’re playing a video game, the game needs to know when you’ve won or lost.

These examples all use instances of decision making. Think of it like a computer being able to answer yes or no, correct or incorrect, or more specifically, True or False. Programming languages have a data type called a boolean that represents the values True and False. The study of computing logical expressions is known as boolean logic. Logical expressions in programming result in either a True or False answer. Let’s revisit the examples above:

• If I sign into Instagram with a my username but an invalid password, will I see my feed? True or False?
• If I type in my birthday, May 24, 1990 when viewing a mature game on Steam, will I be able to see it? True or False?
• If I’m playing Skyrim, and my health goes below 0, do I lose? True or False?

Just as math has arithmetic operators (+ - * /), Python has two categories of boolean operators: comparison operators and logical operators. We won’t cover every logical operator in this lesson, but there is more to come.

Here is a brief rundown of the various operators: equality ==, inequality !=, greater than (>), less than (<), greater than or equal to (>=), less than or equal to (<=), and not (not). Logic expressions can be constructed using different data types combined with these operators. The result will be either true or false. Here’s an example:

1000 == 1000

Is 1000 equal to 1000? It is, so the result is the value True. You can see a number of different examples in the tables below. These are known as truth tables.

Equal To (==)	Result
100 == 100	True
100 == 99	False
"abc" == "abc"	True
"ABC" == "abc"	False
True == True	True
True == False	False

Not Equal To (!=)	Result
100 != 100	False
100 != 99	True
"abc" != "abc"	False
"ABC" != "abc"	True
True != True	False
True != False	True

Greater than/Less than (>,<)	Result
100 > 100	False
100 > 99	True
0 < 100	True
0 < -1	False

Greater than or equal to/Less than or equal (>=,<=)	Result
100 >= 100	True
100 <= 99	False

Not (not)	Result
not True	False
not False	True
not (100 > 100)	True

Skills to Practice

• Constructing boolean expressions using the following operators:
  • Equality (==) and inequality (!=)
  • Greater than (>) and less than (<)
  • Greater than or equal to (>=) and less than or equal (<=)
  • Not (not)

Instructions

Setup

1. Create a new Python application. Name the project 2.1 Logic.
2. Click Create.

Code

name = "Mr. Mortimer"
age = 30
bank_account = 150
is_a_teacher = True
is_a_millionaire = False

print(f"Is my name Mr. Mortimer? {name == 'Mr. Mortimer'}")
print(f"Is my name Mr. Mertens? {name == 'Mr. Mertens'}")
print(f"My name is not Mr. Merriman: {name != 'Mr. Merriman'}")

print(f"Am I old enough to drive? {age >= 16}")
print(f"Do I have enough to buy a Dodge Challenger? {bank_account > 31000}")

print(f"{name} is a teacher: {is_a_teacher == True}")
print(f"{name} is a millionaire: {is_a_millionaire}")
print(f"So, {name} isn't a millionaire? {not is_a_millionaire}")

Debug

Is my name Mr. Mortimer? True
Is my name Mr. Mertens? False
My name is not Mr. Merriman: True
Am I old enough to drive? True
Do I have enough to buy a Dodge Challenger? False
Mr. Mortimer is a teacher: True
Mr. Mortimer is a millionaire: False
So, Mr. Mortimer isn't a millionaire? True

Tips, Tricks, and Reflection

• This demo is not of much use yet. Over the next few activities, you will see just how powerful logical expressions can be in decision making.
• You can quickly test out a boolean expression using the REPL console.